Electrolytic apparatus



Filed Sept. 17, 1932 2.S hee 1 s'-Sheet 1 mv zufon e e i a ATTORNEYPatented Aug. 8, 933

UNITED STATES 1,921,377 I ELECTROLYTIC APPARATUS Louis E. Ward, Midland,Mich.', assignor to The 1 Dow Chemical Company, Midland, Mich., aCorporation of Michigan Application September 17 195%2 Serial NP.633,547

, 12 Claims. (01. 204 -19) The invention relates to apparatus forelectrolyzing a fused salt bath to produce a metal lighter than theelectrolyte, more particularly a bath containing magnesium chloride topro- 5 duce magnesium. 4

The products of such electrolysis, e. g. magnesium and chlorine, bothrise to the surface of the bath and must be separately-collected andremoved to prevent recombination thereof. It

1 has been the usual practice to provide an electrolytic apparatusconsisting essentially of an iron or steel vessel to contain theelectrolyte and to act as cathode, one or more, graphitized carbonanodes depending in the bath in the vessel, and a non-conductingpartition of refractory ma-' terial dipping into the bath between theanode and cathode to separate the anode and cathode products at thesurface of the bath. This simple form of structure has certain inherentdefects which give rise to operating difiiculties and also undulyincrease the power consumption per unit of product. The refractorypartitions are fragile and subject to frequent breakage, necessitatingreplacement thereof, which interrupts -regular operation of the cell.This is especially a serious problem in the larger sizes of cells.Various designs of composite or sectional partitions have been proposed,none of which, however, have succeeded in overcoming the defects of thisstructural element.

Another disadvantage of the aforesaid cell structure, in which thevessel itself is the oathode, is that the electrode surfaces are ofnecessity spaced relatively far apart in order to prothe electrolysis atthe surface of the bath. It is desirable to bring the electrode surfacescloser together in order to shorten the current path through the bath,thereby reducing. the electrical resistance of the cell andconsequentlythe power consumption per unit of product. Various proposalshave been made for accomplishing-this result, e. g. by inserting asupplemental cathode in the cell between the walls of the vessel and theanode or anodes, but in all such of which I am awarethe result has beensimply to reduce the available space at the surface of the bath betweenthe active electrodes for separating anode and cathode products, thusmaking such separation more diflicult. 1

It is an object of the present inventionto provide a novel form ofcathode which, when incorporated in a cell structure of the type inhand, enables the rapid removal from the active zone of the light metalas it is formed on the cathode, such removal being accomplished to'agreat extent before the metal rises to the surface of the bath. Themetal thus removed is collected by suitable means in the inactive zonebetween the between the electrodes. -the removal'of the metal productof' the elec-' I vide for separately taking off the products of 'tenedthereto by welding at one edge of the strips.

cathode and the walls of the vessel where it may.

be kept out of contactwith the gaseous anode products without necessityfor providing any separating partition between the activeelectrodes.

My. improved cathode, therefore, makes possible dispensing entirely withthe useof a fragile partition of non-conducting refractory materialSince with such cathode trolysis from the-active zone takes placelargely below the surface of the bath, the cathode may be advanced moreclosely to the anode surface than is possible'with other types ofcathodes. heretofore described without loss of current eificiency due tointermixing and recombination of anode and cathode'products. Thereby ismade possible a reduction of the electrical resistance of the cell andan increase 'of its energy efficiency. The improvement is set forth inthe accompanying drawings and following detailed descriptionillustrating various forms of structure embodying the principle of theinvention.

In the drawings:--- v Fig. 1 is atransverse section of an'electrolytic'cell structure for a fused bath in which .one

embodiment of my improved cathode is shown. Fig. 2 is a longitudinalsection of a cell similar to the one shown in Fig. 1, having a pluralityof anodes. Fig. 3 is a cross-section of a cell showing a plurality ofanodes in parallel rows in which the an'odes are shown with associatedcathodes individually circumscribing them. Fig. 4 is a partial plan viewof the cell shown in Fig. 3.

' Referring to Fig. 1 of the drawings, the cell shown comprises an ironor steel vessel 1 tocontain a fused salt bath, e. g. containingmagnesium chloride, which constitutes the electrolyte, and a cathodestructure 2 on either side of a graphitized carbon anode 5. Vessel 1 isprovided with an external flange 6, the-edge of which "is upf turned, asshown, forming an L-"section. A suit- 10.

.30? steel plate welded tothe wall of vessel 1 and to cathode 2'. On theinner surface of the cathodes 2 are attached a plurality of strips orbars '10 at an angle with the plate, which may be fas- Strips 10 formwith the plate a plurality of inverted troughs 11 ranged one above theother. Troughs 11 are provided with one or more ports 12- through'theplate affording communication from the trough to the inactive zonebetween'the cathode and the wall of vessel 1.

Vessel 1 is suspended in a furnace setting 13,

a bearing plate 14 being provided .upon' which rests the externalflangeB of the vessel. A-course of heat-insulating refractory material 15 supported andheld in place by flanges 6 and B-forms a lining for acentral anode chamber 16 above cathode 2. Chamber 16 is closed'byacover'll having a central opening through which anode 5 depends, and asecond opening to which is 'con-' tric current is passed through thebath betweenthe electrodes. Chlorine is formed at the anode surface andrises through the bath into chamber 16 whence it is led oil? throughduct 18. Magnesium forms on the cathode surface in small droplets whichbecoming detached rise through the bath and are caught and entrapped bythe inverted troughs 11., The metal entrapped in troughs 11 is forcedout through ports 12 by the hydrostatic head of 'the bath into theinactive space back of the cathode, where it is protected from contactwith chlorine and rises to accumulate as a liquid mass in the invertedtrough 19 under flange 8,' whence it may be withdrawn by means shownmore particularly in Fig.2.

Fig. 2 shows'in longitudinal section a cell similar to that illustratedby Fig. 1, but employing a plurality of anodes in a row. Like referencecharacters refer to similar parts as in Fig. 1. The elongated vessel 1to contain the electrolyte has a row of anodes 5 depending therein, saidanodes being flanked on either side by a cathode 2 having onits faceaplurality of inverted troughs 11 from which ports 12 give access to.the inactive space back of the cathode. Flange 8,-whic h forms theinverted trough 19 for collecting metal rising,

from the ports 12 of the cathode, is carried around the rim of thevessel at one: end and on both sides to -a point near the other end,where it bridges across from side to side ofthe vessel, leaving an openspace 20 at the end which forms a metal collectingwell. In the bridgesection of inverted trough 19 anopening 21 in the side of the troughallows molten metal. to flow from the trough into the well 20 where itaccumulates in a largebody 2011 from which it may be removed by dippingwith a ladle or by other means. A cover 22pmtects the metal in well 20from the air. The anode chamber 16 is enclosed by. the wall ofinsulation material 15, which in turn is supported by flanges 6 and 8,the chamber being closed by cover plates 17, through which-exit. pipe-18 for anode gases is taken 01!. The operation of the cell is asdescribed in the case of Fig. 1. The molten salt bath containingmagnesium chloride is maintained at a level. aboutas shown in thedrawings. Metal formed on the submerged cathode 2"is first entrapped introughs'11' as it rises in small globules from theactive cathodesurface; and thence passes throughports 12, rises throughzthe bath inthe inactive zone back of cathode 2, is collected in inverted trough 19,and from the latter is' forced by the hydrostatic head of the baththrough port 21 into collecting well 20. v

For cells of large capacity a plurality of rows of anodes may be used,one arrangement of which, shown in detail in Figs. 3 and 4, provides twoparallel rows of anodes disposed in staggered relation to each other,each anode individually circumscribed by a cathode. Fig. 3 is across-sec- I tion on the line 3-3 of Fig. 4. Fig. 4 is a partial planview on the line 4-4 of Fig. 3, showing a number of anodes andindividual circumscribing cathodes. 1

In Figs. 3 and 4 a plurality of anodes 5 each circumscribed by a cathode2- are arranged in two parallelrows running lengthwise-in an elongatedvessel 1 having an upturned externally flanged rim 6 and an internallyprojecting flange 8, the latter having a downturned edge forming aninverted trough 19 along the upper edge of the vessel to retain themetal thereinto from the ports 12 of the cathodes 2. Cathodes 2 consistsof hollow shells with upright side walls, preferably tapered downwardlyas shown, having on their inner face a plurality of peripherallydisposed inverted tro ughs 11 ranged one above .the other in themannershown in Figs. 1 and 2. The cathodes 2 may be attached by weldingto the flange 8, alternately on opposite sides of vessel 1, the flangebeing cutout on an arc to give a sufllciently wide bearing surface forwelding the cathode thereto, and are additionally supported by brackets9 connecting to the side wall of vessel 1 through which current isconducted to the cathodes. Theinverted troughs 11 on the inner face ofcathodes 2 are preferably inclined slightly from the horizontal towardthe adjacent side wall of the vessel 1, and a single port 12 located atthe high point of the trough serves to deliver the molten metaltherefrom into the inactive zone back of the cathode. In the operationof such cell the metal formed at-the cathodes, entrapped in Y troughs 11and expelled therefrom through ports 12 rises in the inactive spacebetween the cathodes and the wall of the vessel 1 and accumulates incollecting trough 19 under flange 8, whence it is forwarded continuouslyto a collecting well as shdwninFig. 2.

, Other arrangements of apparatus embodying the principle-of myinvention may be devised, as will readily appear to those versed in theart, and it is understood that the invention comprehends all suchequivalent forms of construction. For example, one, two or more rows ofanodes may be employed, as desired, inaccordance with the size andcapacity of-the cell. The type of cathode herein described, which issubmerged in ,the bath, may be located in close proximity to adownwardlytapering typ'e of cathode is employed, a further advantage accrues, inthat the taper of the cathode corresponds more or less to the naturalwear of the anode in service. Thereby the anode is caused to wear moreuniformly, and at the same time less rapidly, while.

'the tendency to necking down and breaking off, which exists when wearis uneven, is largely avoided.

Other modes of applying the principle of my invention may be employedinstead of those explained, change being made as regards the apparatusherein disclosed, provided the means stated by any of the followingclaims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly'claimas myinvention:---

1. In an apparatus for electrolyzing a fused bath to produce a metallighter than the electroand means to deliver such lyte, a

cathode adapted to ooact with a vertical anode, said cathode having onits face opposed to such anode a plurality of inverted troughs rangedone above the other and adapted to entrap molten metal rising from theactive cathode surface, entrapped metal to a collecting zone therefor.

2. In an apparatus for bath to produce a metal lighter than theelectrolyte, the combination of a metallic vessel to contain'such bath,one or more vertical anodes depending therein and a cathode having onits face opposed to such anode or anodes a plurality of'inverted troughsranged one above the other and adapted to entrap molten metal risingfrom the-active cathode surface and ports in said inverted troughsthrough which to deliver such entrapped metal to a collecting zonetherefor.

3. In an apparatus for electrolyzing a fused bath to produce a metallighter than the electrolyte, the combination of a metallic vessel tocon tain such bath, a plurality of vertical anodes depending therein ina row, and a cathode submerged in the bath on either side of said row ofanodes having on its face opposed to said anodes a plurality of invertedtroughs ranged one above the other and adapted to entrap molten metalrising from the active cathode surface and ports in said invertedtroughs through which to deliver entrapped metal to a .collecting zonetherefor.

4. In an apparatus for electrolyzing a fused bath to produce a metallighter than the electro-- lyte, a cathode having upright sidewallsadapted substantially to enclose a vertical anode, such cathode having aplurality of inverted troughs ranged one above the other on 'the irmerface thereof adapted to entrap molten metal rising from -the activecathode surface and means to deliver such entrapped metal to acollecting zone therefor.

5. In an apparatus for electrolyzing a fused bath to produce a metallighter than the electrolyte, a cathode having upright sidewalls adaptedsubstantially to enclose a vertical anode, such cathode having aplurality of inverted troughs ranged one above the other on the innerface thereof adapted to entrap molten metal rising from the activesurface of the cathode and ports in each trough through which entrappedmetal is delivered to a collecting zone.

' 6. In an apparatus for electrolyzing a fused bath to produce a metallighter than the electrolyte, a cathode consisting of a hollow metallicshell having a plurality of inverted troughs disposed peripherally onthe inner face thereof, and a port through the shell wall in each ofsaid troughs. v

'1. In an apparatus for electrolyzing a fused bath to produce a metallighter than the electrolyte, a cathode consisting of a hollow metallicshell having a plurality of peripherally disposed inverted troughs onthe inner face thereof, said inverted troughs being inclined slightlyfrom the horizontal, and a port through the shell wall in each trough atthe high point thereof.

8. In an apparatus for electrolyzing a fused bath to produce a metallighter than the electrolyte, a cathode consisting of a hollow metallicshell with downwardly converging walls having a plurality ofperipherally disposed inverted electrolyzing a fused' troughs on theinner face thereof, said inverted troughs being inclined slightly fromthe horizontal, and a port through the shell wall in each trough at thehigh point thereof.

9. In an apparatus for electrolyzing a fused bath to produce a metallighter than the electrolyte, the combination of a metallic vessel tocontain such bath, one or more vertical anodes depending therein, acathode in the .form of a hollow shell circumscribing each anode inspaced relation therefrom,'said cathode having on its inner face aplurality of peripherally disposed in-. verted troughs adapted to entrapmolten metal rising from the active cathode surface and ports throughthe shell wall in each trough through which such entrapped metal maypass outwardly from said cathode, and means to collect the metal passingthrough said ports and rising therefrom in the bath. I

10. In an apparatus for electrolyzing a fused bath to produce a metallighter than the electrolyte, the combination of a metallic vessel tocontain such bath, one or more vertical anodes depending therein, acathode in the form of a hollow shell circumscribing each anode inspaced relation therefrom, said cathode having on its inner face aplurality of peripherally disposed inverted troughs inclined slightlyfrom the horizontal and adapted to entrap molten metal rising from theactive cathode surface and a port through the shell wall in each troughat the high point thereof permitting such entrapped metal to passoutwardly, from said cathode, and means to collect the metal passingthrough said ports and rising therefrom in the bath. 4 l 110 11. In anapparatus for electrolyzing a fused bath to produce a metal lighter thanthe electrolyte, the combination of a metallic vessel to contain suchbath, one or more vertical anodes depending therein, a cathode in theform of a hollow shell with downwardly converging walls circumscribingeach anode in spaced relation therefrom, said cathode having on itsinner face a plurality of peripherally disposed inverted troughsinclined slightly from the horizontal and adapted to entrap molten metalrising from the active cathode surface and a port through the shell wallin each trough at the high point thereof permitting such entrapped metalto pass outwardly from said cathode, and means to collect the metalpassing through said ports and rising therefrom in the bath.

12. In an apparatusfor electrolyzing a fused bath to produce a metallighter than the electrolyte, the'combination. of a rectangular metallicvessel to contain such bath, two parallel rows of anodes dependingtherein in alternate arrangement, a cathode in the form of a hollowshell circumscribing each anode in spaced relation therefrom, saidcathode having on its inner face a plurality of peripherally disposedinverted troughs adapted to entrap molten metal rising from the activecathode surface, said troughs being inclined slightly from thehorizontal in a direction toward the adjacent sidewall of said vessel,9. port through the cathode shell in eachtrough on the side adjacent tothe wall of said vessel, and means to collect the molten metal passingthrough said ports and rising therefrom in the bath.

LOUIS E. WARD.

